Polypropylene can be classified into atactic, syndiotactic, and isotactic propylene according to its three-dimensional structure. In general, commercially available polypropylene is isotactic polypropylene, and has excellent mechanical properties due to its high crystallinity, but has the shortcoming of reduced impact resistance.
Accordingly, adding rubber such as ethylene-α-olefin copolymer can improve impact resistance. However, the poor compatibility of the rubber with polypropylene may lead to a whitening phenomenon under external pressure or impact, and this may lead to inferior appearance.
Conventionally, a polypropylene resin composition is used, which is manufactured using propylene polymer having weight average molecular weight of about 10,000 to 100,000 g/mol, and it has excellent fluidity. When the content of the low molecular weight polypropylene resin is relatively high, the appearance may be excellent, but it suffers from reduced impact resistance.
Further, a polypropylene resin composition is used, which is manufactured using atactic polypropylene having weight average molecular weight of about 20,000 to 200,000 g/mol, but there is a limit to how much one can improve its impact resistance due to its low weight average molecular weight.
Thus, there is a need for a polyolefin resin that can improve polypropylene's mechanical properties and also enhance its impact resistance.
The above information disclosed in this Background section is only for enhancing the understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.